'use strict';

function getCIDRSuffix(mask, protocol = 'ipv4') {

const isV6 = protocol === 'ipv6';

const bitsString = mask

.split(isV6 ? ':' : '.')

.filter((v) => !!v)

.map((v) => pad(parseInt(v, isV6 ? 16 : 10).toString(2), isV6))

.join('');

if (isValidMask(bitsString)) {

return countOnes(bitsString);

} else {

return null;

}

}

function pad(binaryString, isV6) {

const groupLength = isV6 ? 16 : 8;

const binLen = binaryString.length;

return binLen < groupLength ?

`${'0'.repeat(groupLength - binLen)}${binaryString}` : binaryString;

}

function isValidMask(bitsString) {

const firstIndexOfZero = bitsString.indexOf(0);

const lastIndexOfOne = bitsString.lastIndexOf(1);

return firstIndexOfZero < 0 || firstIndexOfZero > lastIndexOfOne;

}

function countOnes(bitsString) {

return bitsString

.split('')

.reduce((acc, bit) => acc += parseInt(bit, 10), 0);

}

module.exports = {

getCIDRSuffix

};